Trends and Interannual Variability of Surface Layer Temperature in the Indian Sector of the Southern Ocean Observed by Japanese Antarctic Research Expeditions

摘要

Interannual temperature variation of surface layer (0-400 m) is examined from 12 years (1983-1995) of XBT data obtained by Japanese Antarctic Research Expeditions in the Indian sector of the Southern Ocean. To extract interannual variation, the effect of positional differences in data sampling points is corrected by using the World Ocean Atlas 1994 climatological field. Statistical analysis is made to verify the reliability of the correction qualitatively, and the ambiguity of the obtained signal is discussed. Significant warming trends of 0.02-0.04℃/year are observed at depths of 200-400 m in the western region (50°-90°E, 58°-61°S) from both the observed and positionally corrected time series. Besides these trends, variations of 4-5 year cycles are suggested. The fluctuations at most of the levels except 50-150 m show similar patterns to that at the surface. The effects of different dynamics are suggested in the Winter Water layer.